Displacement ventilation systems are in wide spread use in the HVAC industry. One particular application for such systems is in educational buildings. Typically, a number of displacement air terminal devices will be located along a perimeter wall of a classroom space and are configured to deliver ventilation air to the space, see FIG. 1.
Displacement ventilation (DV) is an air distribution system designed to simultaneously improve indoor air quality and reduce energy use. Cool, rather than cold supply air is provided directly to occupants through low mounted diffusers. Heat generated by the occupants and equipment in the space causes ventilation air to be naturally drawn up by convection which ensures fresh air is continually delivered to the breathing zone of the occupants. The warm air continues to rise and contaminants are carried away towards the ceiling exhaust, resulting in improved indoor air quality near the occupants. Schools, restaurants, theaters, atria, other open spaces with high ceilings, and spaces where air quality is a concern are excellent applications.
In addition to the displacement function, it is also known to configure displacement devices to have induction nozzles. By adding induction, room air from the space can be conditioned, filtered, and returned to the space in a mixture with the ventilation air. This type of unit is sometimes referred to as an induction-displacement unit. In this type of system, a coil is provided in the return air path of the induction-displacement unit to condition the return air, as necessary. In the cooling mode, the coil will reduce the return air temperature to a few degrees below the space temperature. In the heating mode, the coil may be set to raise the temperature of the return air such that the delivered air has a higher temperature than that of the air in the room.
In each mode a space temperature set point can be maintained, however, in heating mode, the induction-displacement unit can no longer function as a displacement terminal unit due to the fact that the delivered air starts rising as soon as it leaves the unit instead of pooling across the floor. To prevent placing an induction-displacement unit in the heating mode, a separate heating system can be provided in the space, such as fin-tube radiation or radiant panels. However, as the induction-displacement units are placed along at least one wall of the space, such heating systems cannot be placed in the same location. This is especially troublesome where the induction-displacement units are located along an exterior wall of the space because this is the location where heating is generally most needed. As such, improvements are desired for induction-displacement units that can simultaneously provide heating to an exterior wall of a space and provide displacement ventilation air to the occupied area of the space.
Representative of the art is U.S. Publication No. 2012/0270494 which discloses an induction-displacement neutral wall air terminal unit includes a housing defining a supply airflow path, a connected return airflow path, and a heating airflow path separated from the supply and return airflow paths by at least one interior wall. The unit also includes a plurality of induction-type nozzles located within the supply airflow path, that are deliver a ventilation air flow stream into the supply air flow path. The nozzles induce a return air flow stream through the return air flow path that mixes with the ventilation air flow stream to form a supply air flow stream delivered to a supply air outlet. A heating element is disposed within the heating airflow path to heat air within the heating air flow path. A plurality of fans may be placed within the heating airflow path to increase the overall heating capacity of the unit.
What is needed is an induction displacement unit comprising an induction plenum communicating with a first discharge plenum and a second discharge plenum, the first discharge plenum in communication with a heating coil and the second discharge plenum in communication with a cooling coil. The present invention meets this need.